Locking devices

ABSTRACT

The invention is concerned with providing a hydraulically operated device for locking two relatively movable parts together in a manner which is not disturbed by loss of hydraulic pressure due to failure or shut-down of the machine, the device comprising a toggle-joint which is driven over and back across the dead point by hydraulic pressures, a small section of the movement of the toggle ends being used to take up the play for clamping and the remainder of the movement being used to compress an energy storage device to provide sustained clamping forces.

United States Patent [1 1 Guilleray 1 July 17, 1973 LOCKING DEVICES Roger Guilleray, La Haye Les Roses, France [75] Inventor:

[30] Foreign Application Priority Data Sept. 15, 1970 France 7033421 [52] US. Cl. 29/1 A, 188/265 [51] Int. Cl B23q 1/28 [58] Field of Search 29/1 A; 269/201, 269/228; 74/520; 188/265; 60/7 [56] References Cited UNITED STATES PATENTS 2,955,347 10/1960 Zajac 29/l A Z I? l/ 2,049,842 8/l936 Kling 39/l A Primary ExaminerFrancis S. Husar Attorney- Brenner, OBrien et al.

[57] ABSTRACT The invention is concerned with providing a hydraulically operated device for locking two relatively movable parts together in a manner which is not disturbed by loss of hydraulic pressure due to failure or shutdown of the machine, the device comprising a togglejoint which is driven over and back across the dead point by hydraulic pressures, a small section of the movement of the toggle ends being used to take up the play for clamping and the remainder of the movement being used to compress an energy storage device to provide sustained clamping forces.

4 Claims, 4 Drawing Figures PATENTELJUL 1 7191s SHEET 3 [IF 3 LOCKING DEVICES The invention relates to a locking device intended to secure the different sections of a machine tool into a relative pre-determined position for a long period of time.

It is necessary to be able to lock the different sections of a machine-tool, with respect to each other, for a long period of time, in such a way that an operation may be broken off, for example at the end of the week and then resumed without having to adjust the machineagain. Such a locking device must, at the same time be strong and stable.

A hydraulic locking device of the conventional type, is not suitable as the pressure must be maintained while the operation is stopped which necessitates, for example, the functioning of a compressor while the operation is stopped. In another connection, in the case of the breakdown of the hydraulic device, the moving parts do not retain their respective positions.

The aim of the invention is to provide a locking device for a machine-tool which makes it possible to obtain a strong and lasting locking.

According to' the invention a locking device comprises a hydraulic device acting on a toggle-joint (knuckle-joint) which can go over a dead point, a small section of the toggle-joint serving to take up the play between the sections to be locked, the remainder of the stroke serving to compress a device for storing energy.

According to a further feature of the invention, the body of the device is fixed on one of the sections to be locked and the aforementioned moving part bears against a locking part coming into contact with the second part to be locked.

According to a further feature of the invention, the body is secured, in a sliding manner, onto one of the sections to be locked and is integral with the second part to be locked and the said moving part is in abutment against the first part to be locked.

According to one embodiment of the invention, one of the ends of the toggle-joint is lodged in the body of the device and the other bears against a part forming a push rod acting on a moving part through the intermediary of one or several Belleville (dished) spring washers.

The invention is described hereinafter with reference to the accompanying drawing in which:

FIG. 1 shows a sectional view of a locking device according to the invention,

FIG. 2 shows a locking system operated using the device of FIG. 1,

FIG. 3 shows a locking system by traction using the device of FIG. 1 and,

FIG. 4 shows a safety device.

The device described in FIG. 1 comprises a housing 2 in which a mechanism for the toggle-joint 3 is located, the toggle-joint comprising two levers 4 and 5 pivoted with respect to each other about an axis 6. The two ends of the toggle-joint 3 have a rounded shape; one of these ends, referred to at 7, is located in a housing corresponding to the housing 2, and the other end, referred to at 8, is located in a circular socket arranged in the part 9, which part 9 forms a push rod and slides in the housing 2.

The toggle-joint 3 is actuated by means of a cylindrical piston which is displaced in a cylinder 13 and in the axis of which there is arranged a recess 10 in which the by pressure toggle-joint 3 can be moved. This recess 10 is defined, by two sections 11 and 12 of the piston which are V- shaped, in such a manner that the piston is always in contact with the axis 6 of the togglejoint. The housing 2 comprises two inlets l4 and 15 for fluid, making it possible to apply a hydraulic pressure onto one or other of the external faces of the piston.

The stroke of the piston is such that the toggle-joint can pass from an open position shown in FIG. 1 and diagrammatically in 3' in FIG. 4, into a locking position shown diagrammatically in 3" in FIG. 4 in which the toggle-joint has just exceeded the dead point.

The part 9 forming the push rod comprises a cylindrical bore arranged at the bottom of the socket of the lever 5 and in which is located a close-coil spring 16 urging together the parts 4, 5 and 6 of the toggle-joint 3 in the released position, i.e., in the open position. This push-rod 9 acts on a moving part 17 by the intermediary of a device for storing energy operating under the pressure advantageously constituted by several Belleville washers 18.

The functioning of the device which has just been described is as follows. When a locking pressure is applied via the aperture 14, the piston is displaced to the lower part by abutment causing the toggle-joint to pass over its dead point. This results in the end 8 of the togglejoint 3 being displaced towards the left and driving the push-rod 9. The latter pushes the moving part 17 by the intermediary of Belleville washers 18; when the moving part 17 can no longer be displaced, the remainder of the movement of the push-rod 9 is absorbed by the Belleville washers 18 which create a locking pressure.

The opening is attained by applying a pressure at the aperture 15. Then the piston bears against the axis 6 in such a manner as to cause the toggle-joint to pass over the dead point and to return to the open position shown in FIG. 1.

FIG. 2 shows a system for locking the table of a milling machine on its bracket. In this case, the housing 2 of the device of FIG. 1 is fixed, for example by screwing onto the bracket 21. The moving piece 17 acts on the end of a sliding rod 22, the other end of which is integral with a wedge-shaped part 23 which can come into contact with a corresponding face 24 of the plate 25. The play between the part 23 and face 24 corresponds to a small section of the stroke of the push-rod 9. For example, this play is equal to 0.1 mm whereas the stroke of the push-rod 9 is 1 mm. Thereby, 9/10 of the stroke of the push-rod 9 serve to compress the Belleville washers 18 and thus to create a locking pressure. For example, a locking force of about two metric tons can be attained by using a drivinghydraulic pressure of about 47 bars.

FIG. 3 shows a locking system for the ram of a milling machine with respect to its frame. In this case the housing 2 of the device of FIG. 1 is mounted forsliding motion in the frame 31, the housing 2 is integral with an intermediate part 32 fixed at one end of a moving rod 33 the other end of which is integral with the ram 34 by the intermediary of a locking part 35. The latter has a shoulder 36 which may come into locking contact with a part 37 of the frame.

In the intermediate piece 32 cylindrical parts 38 are located in free sliding motion. These cylindrical parts 38 are distributed regularly around a circle on the part 32; they can for example be in the number of three and located at One of the ends of the parts 38 is in contact with the moving part 17 and the other is in contact with the frame 31, preferably by the intermediary of a wide washer 39 to prevent the deformation of the bed of the frame, which is not resistant enough.

In this case, the locking is brought about not by pressure but by traction. Indeed, when the push-rod 9 bears against the moving part 17, the whole of the body 2 slides onto the frame while pulling the part 36 which comes into contact with the part 37. When the part 36 is taken up the play which existed, for example 0.1 mm, the remainder of the stroke of the push rod 9 is absorbed by the Belleville washers l8 and that creates the locking force.

It can be seen that it is sufficient to apply locking or opening pressure during the time necessary for the toggle-joint to move and that the driving fluid pressure can then be released. Due to the fact that the toggle-joints passes over the dead point, the locking force is maintained in a lasting manner.

The locking device, moreover has the following advantages.

The hydraulic pressure only being used when a locking or opening operation is carried out, there is no strain on the hydraulic system.

In another connection, the toggle-joint having a low clearance angle, makes it possible to magnify the locking force enabling the driving hydraulic force to be small in size in the system which, of course, may sometimes be extensive when installed in complex or multiple machines.

Advantageously, since the order of locking is not necessarily maintained, the locking device according to the invention comprises a safety device preventing all driving movement of the locked parts until the opening has taken place. This safety device can be constituted by an electric switch of the microswitch type, preventing all driving movement when the device according to the invention is in a locked postion.

In the embodiment shown in FIG. 4 the moving part 41 of this electric switch 42 is integral with the free end of the lever 4 of the toggle-joint in such a manner as to be turned with the latter.

I claim:

1. A hydraulically operated device for locking a movable part of a machine tool with respect to a relatively fixed part thereof comprising:

a toggle joint arranged between said relatively movable pans of said machine tool and movable on either side of a dead point between a first position near thereto wherein said movable part is loaded with a high clamping force and thereby locked on said fixed part and a second position relatively spaced from the dead point wherein said movable part is released and capable of moving with respect to said fixed part, and,

a hydraulic actuating device for moving said toggle joint between said first and second positions, said device comprising a double acting piston having two axially spaced annular sections sealingly slidable within a cylinder to define therein two variable volume chambers, respectively, a recess being provided between said sections for receiving the main portion of said toggle joint and for actuating same from one to the other of said positions depending upon one or the other of said variable volume chambers being connected to a fluid pressure source or to a reservoir, respectively.

' 2. A hydraulically operated device according to claim 1, wherein an energy storing device is arranged in series relationship with said toggle joint between said fixed and movable parts of the machine tool.

3. A hydraulically operated device according to claim 2, wherein said energy storing device is comprised of a stack of resilient dished washers.

4. A hydraulically operated device according to claim 3, wherein said toggle joint is comprised of two levers pivotally connected to a coupling member arranged therebetween with one of said levers pivotally abutting a radial recess in said cylinder, the other lever being connected to said movable part of the machine tool. 

1. A hydraulically operated device for locking a movable part of a machine tool with respect to a relatively fixed part thereof comprising: a toggle joint arranged between said relatively movable parts of said machine tool and movable on either side of a dead point between a first position near thereto wherein said movable part is loaded with a high clamping force and thereby locked on said fixed part and a second position relatively spaced from the dead point wherein said movable part is released and capable of moving with respect to said fixed part, and, a hydraulic actuating device for moving said toggle joint between said first and second positions, said device comprising a double acting piston having two axially spaced annular sections sealingly slidable within a cylinder to define therein two variable volume chambers, respectively, a recess being provided between said sections for receiving the main portion of said toggle joint and for actuating same from one to the other of said positions depending upon one or the other of said variable volume chambers being connected to a fluid pressure source or to a reservoir, respectively.
 2. A hydraulically operated device according to claim 1, wherein an energy storing device is arranged in series relationship with said toggle joint between said fixed and movable parts of the machine tool.
 3. A hydraulically operated device according to claim 2, wherein said energy storing device is comprised of a stack of resilient dished washers.
 4. A hydraulically operated device according to claim 3, wherein said toggle joint is comprised of two levers pivotally connected to a coupling member arranged therebetween with one of said levers pivotally abutting a radial recess in said cylinder, the other lever being connected to said movable part of the machine tool. 